There has known a liquid crystal display device including picture elements and pixels where touch sensors are provided. The touch sensors of such a liquid crystal display device employ, as a sensing type, an optical sensor type, a contact point (contact) type, or a capacitance type. The three sensing types have been put into practical use.
FIG. 21 shows a configuration of a display region where an optical sensor type touch sensor is provided.
FIG. 21 specifically shows a configuration of the n-th line of a display region of a liquid crystal display panel. In the n-th line are provided (i) a plurality of picture elements PIX defined by a gate wiring Gn, source wirings S (Sm through Sm+3 of FIG. 21), and a retention capacitor wiring Csn, and (ii) at least one sensor circuit (optical sensor circuit) 102 connected to a reset wiring Vrstn and a readout control wiring Vrdn.
Each of the plurality of picture elements PIX includes a TFT 101 serving as a selection element, a liquid crystal capacitor CL, and a retention capacitor CS. The TFT 101 has a gate connected to the gate wiring Gn, a source connected to corresponding one of the source wirings S, and a drain connected to a picture element electrode 103. The liquid crystal capacitor CL is a capacitor formed by the picture element electrode 103 and a common electrode com having a liquid crystal layer therebetween. The retention capacitor CS is a capacitor formed by the picture element electrode 103 or a drain electrode of the TFT 101, and the retention capacitor wiring Csn having provided an electrically insulating film therebetween. For example, a constant voltage is applied to the common electrode com and the retention capacitor wiring Csn.
The number of the sensor circuit 102 to be provided in the display region is optional. For example, the sensor circuit 102 is provided for each of the plurality of picture elements PIX or for each of pixels (for example, for each of pairs of R, G and B picture elements PIX). The sensor circuit 102 includes an output amplifier 102a, a photodiode 102b, and a capacitor 102c. The output amplifier 102a is made up of a TFT. The output amplifier 102a has a gate connected to an electrode herein referred to as a node netA, a drain connected to the source wiring Sm+1, and a source connected to the source wiring Sm. The photodiode 102b has an anode connected to the reset wiring Vrstn, and a cathode connected to the node netA. The capacitor 102c has a terminal connected to the node netA, and the other terminal connected to the readout control wiring Vrdn.
The sensor circuit 102 carries out touch sensing by detecting whether or not a shadow of a fingertip is made by an approach or a contact of the fingertip to a panel during a period other than a period during which data signals are written in the picture elements PIX. A voltage of the node netA is reset by a voltage of the reset wiring Vrstn via the photodiode 102b. Subsequently, the source of the output amplifier 102a outputs therefrom, as a sensor output voltage Vo, a voltage that appears at the node netA in accordance with an intensity of light received by the photodiode 102b, by use of a rise in pressure of the node netA caused by a change in voltage of the readout control wiring Vrdn. The sensor output voltage Vo is transmitted, via a sensor output wiring Vom that is the source wiring Sm+1, to a sensor reading circuit provided somewhere other than the display region. In this case, the output amplifier 102a functions as a source follower. Further, in this case, the source wiring Sm connected to the drain of the output amplifier 102a functions as a sensor power supply wiring Vsm to which a constant voltage is to be applied during light detection.
FIG. 22 shows a configuration of a display region where a contact point type touch sensor is provided.
In FIG. 22, the sensor circuit 102 of FIG. 21 is substituted with a sensor circuit 202.
The sensor circuit 202 includes a readout TFT 202a and a switching electrode 202b. The readout TFT 202a has a gate connected to a readout signal wiring Vrdm, a drain connected to a first electrode of the switching electrode 202b, and a source connected to a sensor output wiring Vom. The switching electrode 202b has a second electrode constituted by a common electrode com to which a voltage Vcom is to be applied.
In the sensor circuit 202, the first electrode of the switching electrode 202b contacts the second electrode of the switching electrode 202b in response to a pressure applied to a panel by a fingertip, to form a contact point. In this case, the readout TFT 202a is switched on by a voltage applied via the readout signal wiring Vrdm during a period other than a period during which data signals are written in picture elements PIX. This allows the voltage Vcom to be supplied to the sensor output wiring Vom via the switching electrode 202b and the readout TFT 202a. It is therefore possible to carry out touch sensing.
FIG. 23 shows a configuration of a display region in which a capacitance type touch sensor is provided.
In FIG. 23, the sensor circuit 102 of FIG. 21 is substituted with a sensor circuit 302.
The sensor circuit 302 includes an output amplifier 302a, a photodiode 302b, and capacitors 302c and 302d. The output amplifier 302a is made up of a TFT. The output amplifier 302a has a gate connected to an electrode referred to as a node netA, a drain connected to a source wiring Sm, and a source connected to a source wiring Sm+1. The photodiode 302b has an anode connected to a reset wiring Vrstn, and a cathode connected to the node netA. The capacitor 302c has a terminal connected to the node netA, and the other terminal connected to a readout control wiring Vrdn. The capacitor 302d has a terminal connected to the node netA, and the other terminal constituted by a common electrode com.
The sensor circuit 302 carries out touch sensing by detecting, during a period other than a period during which data signals are written in picture elements PIX, a change in capacitance value Ccvr of the capacitor 302d, which change is caused by a pressure applied to a panel by a fingertip. The photodiode 302b is provided for causing the sensor circuit 302 to operate as an optical sensor circuit as with the sensor circuit 102. The photodiode 302b also has a diode property that is utilized for causing the sensor circuit 302 to operate as a touch sensor circuit. A voltage of the node netA is reset via the photodiode 302b, and then a voltage of the readout control wiring Vrdn is changed. This causes the voltage of the node netA to have a value corresponding to a value of the capacitor 302c, and the capacitance value Ccvr of the capacitor 302d, which capacitance value Ccvr is determined depending on the pressure. Therefore, a voltage that appears at the node netA is transmitted as a sensor output voltage Vo from the source of the output amplifier 102a via a sensor output wiring Vom that is the source wiring Sm+1 to a sensor reading circuit provided somewhere other than the display region. In this case, the output amplifier 302a functions as a source follower. Further, in this case, the source wiring Sm functions as a sensor power supply wiring Vsm to which a constant voltage is to be applied.
FIG. 24 shows a configuration of a contact point type touch sensor disclosed in Patent Literature 1.
Specifically, FIG. 24 is a cross-sectional view of a liquid crystal display device with which a user's finger or the like is in contact. The liquid crystal display device includes a lower display board 100, an upper display board 200, and a liquid crystal layer 3 sandwiched between the lower display board 100 and the upper display board 200. The lower display board 100 includes an electrically insulating substrate 110, and a pixel layer 115 provided on the electrically insulating substrate 110. The pixel layer 115 includes, for example, pixels and a sensing section. From the pixel layer 115 are exposed input terminal electrodes 196 of sensing elements of a contact sensing section.
The upper display board 200 includes a substrate 210, and light-shielding members 220 provided on the substrate 210. The light-shielding members 220 prevent light leakage between pixels. A plurality of color filters 230 are provided on the substrate 210 and the light-shielding members 220. A cover film 250 is provided on the color filters 230 and the light-shielding members 220 to protect the color filters 230 and flatten a surface of the color filters 230. On the cover film 250 are provided a plurality of projections 240 made from, for example, an organic material. Specifically, the projections 240 are provided so as to face the input terminal electrodes 196 of the sensing elements, respectively. On the cover film 250 and the projections 240 is provided a common electrode 270. The lower display board 100 and the upper display board 200 are supported by a plurality of bead spacers 320. This allows the common electrode 270 covering the projections 240, and the input terminal electrodes 196 to keep having therebetween a constant interval which falls within a range from 0.1 μm to 1.0 μm.
The common electrode 270 covering the projections 240, and the input terminal electrodes 196 constitute a switch of the contact sensing section.
The common electrode 270 covering the projections 240 which is a contact point is electrically and physically connected to the input terminal electrodes 196 of the lower display board 100, in response to a pressure applied to the upper display board 200 by a contact. This causes a common voltage Vcom to be carried to the input terminal electrodes 196, thereby flowing sensing current through the sensing elements.